A conventional bicycle is operated by treading the pedals connected to two ends of the crank and a chain transmits the power from the chainwheel connected with the crank to the sprockets connected to the axle of the rear wheel to move the bicycle forward.
The conventional bicycle can only be operated manually and a derailleur system can be added to the bicycle to increase the efficiency of operation. For the force that the rider applied to the bicycle, once the force is discontinued, there is no assistance device to adjust, store or change the force.